Index: /branches/release-39/lib/MT/CMS/Entry.pm
===================================================================
--- /branches/release-39/lib/MT/CMS/Entry.pm (revision 2454)
+++ /branches/release-39/lib/MT/CMS/Entry.pm (revision 2514)
@@ -1332,8 +1332,11 @@
         $place->category_id($cat_id);
         $place->save;
+        my $cat = $cat_class->load($cat_id);
+        $obj->cache_property( 'category', undef, $cat );
     }
     else {
         if ( $place ) {
             $place->remove;
+            $obj->cache_property( 'category', undef, undef );
         }
     }
@@ -1368,4 +1371,8 @@
           );
         $placements_updated = 1;
+    }
+    if ($placements_updated) {
+        $obj->cache_property( 'categories', undef, [] );
+        $obj->cache_property( 'categories', undef, \@add_cat );
     }